"Manner Legs" is quite a thing in Korea. Usually, it is the main actor that does it for the actress. For example, Kim YoungKwang for Park BoYoung.
The actress is 171 cm tall.
The actor is 182cm.
For the poster shooting, in the behind-the-scenes revealed by SBS. The actress is doing "manner legs" so that the height difference between her and the main actor seems bigger than in reality to have a better picture.
Here is how they look like without the manner legs.
You can have a look at the behind-the-scenes of the poster making below.
What do you think?